Many motor vehicle tires have a circumferential tread provided with a plurality of spaced-apart circumferential grooves that define ribs therebetween. Typically, generally lateral slots can be provided in the ribs to form a plurality of shaped blocks. These shaped blocks can be distributed along the tread according to a specific pattern. Sipes, which are generally narrow slits cut into the tread, can be provided in the shaped blocks in a specific pattern.
Within the tread pattern in which the circumferential grooves are provided, the shaped blocks are typically distributed in several side-by-side rows. A proper distribution of the shaped blocks gives the tire the desired characteristics of directional control stability and road gripping in relation to the sidewise thrusts directed parallel to the wheel axis. The lateral slots, in turn, give the tire the desired traction (i.e., the capability of efficiently transmitting tangential thrusts parallel to the running direction during speeding up and slowing down of the vehicle). In principle, the traction of the tire on snow laden surfaces tends to become greater as the number of the lateral slots arranged in the tread increases and the orientation of the slots themselves approach an orientation that is perpendicular to the running direction of the tire.
Also, sipes provided in a rib or shaped block of a tire can improve snow traction of the tire. For example, as the tire rolls, the sipes present multiple “edges” to the snow-laden surface. These edges can act as fingers to grip the snow, thereby improving traction of the tire in snow. Thus, the more sipes provided in a rib or shaped block, the greater the circumferential edge density of the tire, which results in improved snow traction of the tire.